1. Field of the Invention
The present invention relates to memory devices that use resistive-change memory elements, and fabrication processes of such memory devices.
2. Description of the Related Art
Semiconductor devices that include nonvolatile memory such as EEPROM (Electrically Erasable and Programmable ROM) and flash memory have been commonly used in a wide range of fields.
Improving reliability such as rewrite count and data retention durability, and miniaturization of the memory structure pose significant challenges to the nonvolatile memory.
Resistive-change nonvolatile memory has gained attention as having advantages in reliability and miniaturization over the structure of the currently marketed flash memory as represented by the floating-type structure.
Regarding such resistive-change nonvolatile memory, for example, ReRAM (Resistive Random Access Memory) and PCRAM (Phase Change Random Access Memory) have been proposed (see, for example, JP-T-2002-537627 and U.S. Pat. No. 6,339,544; the term “JP-T” as used herein means a published Japanese translation of a PCT patent application).
The resistive-change nonvolatile memory has a simple structure and high-speed rewrite performance, and is considered suitable for achieving high performance and high integration with the use of multivalue technology.